Television apparatus



Oct. 28, 1941- s. 1.. CLOTHIER ET AL TELEVISION APPARATUS Original Filed July l'7, 193'? 3 Sheets-Sheet 1 STEWART L.. CLOTHIER HAROLD C. HOGENCAMP INVENTORS Rm ATTORNEY s. L. CLOTHIER ET AL TELEVISION APPARATUS Original Filed Ju}.y 1.7, 1937 3 Sheets-Sheet 2 STEWART LI CLOTHIER HAROLD-C. HOGENCAMP [1V VEN T 0R8 .A TTORNEY v Oct. 28, 1 941 s. L. CLOTHIER ET AL 2,260,559

TELEVIS ION APPARATUS Original Filed July 17, 1937 3 Sheets-Sheet 3 /8 INVENTORJ STEWART LCLOTHIER BY HAROLD C. HOGENCAMP ATT R objects of the invention will Patented Oct. 28, 1941 Stewart L. C-lothier,

Hogencamp,

Kolorama Laboratories,

Maplewood,

Irvington, and Harold C.

'N. J., assignors Ito Ina, Newark, N. J.-, a

corporation ofNew Jersey Original application J11 154,218, now Patent N 20, 1939. Divided and 1939, Serial No. 219,568

2 Claims.

1 17, 1937," Serial No. 0. 2,163,538, dated June this application June 16,

This invention relates to television and more particularly to mechanical scanning methods and apparatus.

Cathode ray tubes have been employed in electron-beam scanning apparatus but such use has been attended by certain limitations with F respect to the small size of tube available and the relatively great expense thereof, which limitations have generally precluded the use of a cathode ray tube where a screen of any appreciable size is required. In order to make use of, a larger screen, resort has been made to rotating scanning mechanisms for intercepting the modulated light beam in order that the desired image may be formed to any desired size commensurate with proper light intensity and suit- 5 able definition. At the relatively high speeds of rotation employed to obtain adequate resolution of the image, a certain degree of optical distortion is ordinarily produced by undesirable dynamic forces present in and acting upon the moving parts. For example, where the mirrored drum consists of peripherally mounted plates, rapid rotation of the drum may cause deflection of the plates from their normal position as a result of centrifugal force. Furthermore, the armature of the synchronous motor which drives the mirrored drum, though apparently rotating at a constant speed is subject to electromagnetic pulsations producing variations in torque of sui- :flcient magnitude to set up fluctuations in the speed of rotation of the drum. These and other efiects incidental to the operation of a mechanical scanner may introduce a serious source of distortion in the finally-formed image.

In the present invention, apparatus incorporating novel design principles, many of the factors which detracted from the formation of a satisfactory image have been eliminated. In the present apparatus provisions through the use of 1 have been made which count for high optical efficiency and which eliminate those detrimental characteristics introduced by undesirable fluctuations in the movement of the parts.

Accordingly the principal objects of the present invention are to provide an improved television scanning apparatus incorporating novel design features; to provide in such apparatus means for minimizing undesirable variations in the motion of the parts; to provide improved means for projecting, the image upon a screen to one of several predetermined sizes; and to provide an improved cam-operated mechanism for actuating the frame scanner.- These and other become readily ap- 1 properly oriented calcite blocks or Nicol prisms.-

parent from the following specification in conjunction with the appended drawings.

In the drawings: r Fig. 1 is'a perspective View of a preferred form of televisionscanning apparatus incorporating features of the present invention; f V V Figs. 2, 3, 4 and5 are schematic views illus trating various optical systems which maybe employed with an apparatus of the type dis closed in Fig. 1; Fig. 6 is a plan mechanism; V Fig. 7 is a cross-sectional view'of the frame scanning mechanism takenonthe'line' 1--1 of Fig. 6; a

Fig. 8 is a cross-sectional view through the scanning disc illustrating thehub construction; Figs. 9 and 10 illustrate two forms of plate View of the frame scanning type-cams which may be employed with the identify similar parts throughout the several views.

Referringagain to the drawings, the invention comprises a'source of modulated 'lightL which may be of any conventional form. As shown in Fig. l, the modulated light source comprises a housing H for enclosing a suitable "light source: as ior example an electric arc. The light emerges as a beam from the housing H through a tube T'containing conventional con densing lenses or other means capable of focusing light from the source into 'a luminous spot of concentrated light preferably covering "a square opening or aperture A. 1 A light modulator M is positioned at the extremity of thetu'be 'T and is operative to modulate the light, by varying its intensity in response to the television signals received from the transmitting station. The light modulator M may be of any conventional design, for example, of a type incorporating a Kerr cell in conjunction with a pair of g The modulated light beam B issuesfrom an aperture A'formed in a plate P at the end of the tube T and passes through an objective lens or lens system II which is capable of forming an image of the aperture A. The lens system II is held by means of a collar [2 and may be moved axially in order to vary the position of the image plane within predetermined limits in a manner to be more fullydescribed. Afterpassing through the system II the beam B is devibration and distortion, the disc or drum D is 1,

preferably made of a single piece of uniform quality plate glass I4. The hub I5 is firmly se-' cured within a central aperture'of the glass plate I4, as shown in Fig. 8, preferably as an initial operation inthe fabrication of the disc D. The

hub I is carefully bored so as to form a smooth slidingfit upon the shaft I6 of a motor I1. An,

outer collar I9 and an inner collarare firmly secured on opposite sides of the disc D to the shaft I6, as by means of set screws 23 and 24 and prevent the disc D from shifting axially on the shaft I6. The rotative movement is transmitted to the disc D by means of one or more pins I8 extending axially from the outer collar 1 I9 through registering apertures'2-I- formed in the I-h'ub I5. The apertures 2I are sufiiciently larger than the pins I8 to provide space-fora sleeve 22 of resilient cushioning material, for example, .soft'rubber'. It has been found that through the use of such a resilient sleeve between the pins and'the disc Dthat a considerthe cam to the mirror. The mechanism 36 preferably comprises a hardened steel ball-bearing roller 31 journalled within a yoke 38. The roller 31 is preferably as wide as the cam 35- to provide larger contact area, and to minimize wear. A

follower rod 39 preferably of circular cross-section extends from the yoke 38 through a guide M which permits the roller 31 and the follower rod 39-to'slide freely in an axial direction as the cam rotates. A pivoted guide support 42 is adjustably held within a base member 43 and may be maintained at any desired position asby means of a screw 44.

The frame scanning mirror is firmly secured to a spindle 45, and the spindle is mounted for 7 oscillatory movement within a pair of spaced able amount of torque variation produced by the uneven motion of the armature'and-otherwise transmitted to the disc D is filteredout and eliminated. Although the cushioning motion occasionedby the flexing of the resilient sleeves 22 is relatively slight, it is nevertheless sufiicient to overcome what has heretofore. proven to be a considerable source of distortion in the television The'outer periphery of the scanning disc D is "preferably provided with from 515*to 180plane reflecting surfaces 26 which are formed by :ac curately grinding and polishing the glass -plate I4. These surfaces 26 intercept equal arcs' on the periphery of the disc D and'are all positioned at thesame angle with, and preferably perpen dicular to one face of the plate I4. The number of surfaces employed and the speed-of the motor I1iare determined by'the frequencyof the impulses received from the transmitting-station. The surfaces after-being properly polished are preferably coated with a"refiecting material as "by depositing metallic silver about the periphery of the disc D. ,The coating after being firmly depositedis polishedto mirror brilliance so as -to'be capable of faithfully reflecting the beam B; When the disc D rotates, thebeam B is re flected upon a frame-scanning mirror ;21-as a succession of shifting lightimpulses which after passing through a projection lens 28 are focussed bearing blocks 46. A lever 41 is secured to the spindle 45 as by means of a clamp 48 in such a manner that movement of the lever 41 imparts a pivotal mot-ion to. the mir ror -21 about,the spindle 45 as a fulcrum.. The movementof-the roller 31, imparted by h h a to the lever 41 by means of an adjustable collar 49 and an articulated joint 5Isecuring the collar 49 to the follower rod 39.v A tension 'spring52 engages the. lever 41 and urges thefrollen31 continually against thecam 35." A-Ycamfor example of the type shown in Fig. 9, when rotating with thecam shaft 34 causes the rod 39 toxos'cillate longitudinally, describing simple harmonic motion or any similar predetermined form, of oscillation as incorporated in and gove'rned by the shape of the cam employed. Althoughi'the amplitude ;of the oscillation is governed so e? What by the rise in the cam, the degree .of I I gular oscillation or sweep imparted. to :themir'ror 21 may also be regulated by adjusting thesliding collar 49 on the lever 41.. The required sweep of the mirror-21 is determined by'thedistance of the mirror 21 from the planelofthe image formed by the lens system II, and by the size of the image which is to be forme'cl o'n the, screen S. The position of the collar 49 upon the'lever 41 fora givenset of operatingconditionsmay be determined mathematically of experimentally and when once adjusted may be fixed by means of-a setscrew 53. The guidesupport 42. rria'yfbe raised orlowered as desired so that therod 39 upon a screen S as-a laterally extending line of light. j The successive light.- impulses may be spread. over a predetermined area of the screen S as'a series of adjoining lines by oscillating the mirror 21.

Theapparatus employed for actuating the frame; scanning mechanism is more clearly shown inrFigs. Sand '7 andcomprisesa frame- 1 scanning motor F. having a motor shaft 29.--A

.fiexible' coupling 30 links shaft 29 with apinion shaft 3|, having a pinio'nf32 secured thereto for operativetengagement with a gear 33 mounted :on

1 a'cam'shaft 34; A plate cam 35 is'rigidly' se- "cured to the shaft 34 for rotation therewith; I 'Cam follower mechanism 36 extends between -the?cam.35 .and .the'fra'rriescanning mirror 2-1 and operates to impart oscillatory motion from cam.

the pivoted joint in the support compensate ing for the change in the angular position of the guide 4| inresponse to thelverticaladjust ment The configuration of the cam 35 is determined by the needs of various operating. conditions. In the form of cam indicated in Fig.7 two complete cycles of oscillation 'are imparted tothe mirror 21 during each revolution-fof thecam. Modified cams, of somewhat different shape,]a r'e shown in Figs. 9 and 10 respectively. The cams indicated in Figs. 9 and 10 are intended I20 PIP- vide a scanning motion of the mirror -21 byim; parting uniform or. substantiallyuniform anguQ- lar velocity in one direction during a singleframe scan followed by a quick motion in the opposite direction to return the mirror to the initial posi tion, which return motion is best effected ,in the time interval between successive frames. In the form of cam indicated in Fig. 9, one -complete frame-scanning cycle is effected during each half rotation of the cam, while Withtheforrnof cam shown in Fig. 10 this same cycle ofopelra tionis effected during an entire rotation -o the With a cam of the type matated "iii the cam 35, i's conveyed imparted to the shaft 3! :of the flexible coupling image. wheel 50 secured upon the shaft 34 in close relaorder to obtain 30 separate picturesper second,

it is absolutely essential that the cam rotate evenlly at the intended rate without any fluctuations in speed, and further that chattering between the cam and the follower bev avoided. The latter difliculty may be. quite completely eliminated through the use of a properly designed spring 52, but whenexcessive pressure is exerted. against the roller 31 urging it against the cam surface, the pressure may exert an undesirable influence upon the rate of rotation of the cam. Tests have indicated that this condition ordinarily prevails, and the varying pressure imparted by the rising and falling cam followerexerts retarding and ac- .celeratinginfiuences upon the cam 35 causing the 'cam to undergo undesirable speed fluctuations. -.When gears are employed between the cam shaft and the driving motor this variation in speed may be represented by lost motion in the gearing. Another factor contributing to vari- ,ation inthe speed of the cam 35 is the fluctuations bythe varying torque armature of the motor F, although the materially aids in smoothing outythese variations. In any case, all of .these factors afiect thesmooth operation of the cam and detract from the fidelity of the reproduced However, ,it has been found that anytion to the cam 35,0perates to smooth out such fluctuations and to materially improve thequality of the reproduced image. be keyed or otherwise rigidly secured to the shaft 34 to prevent any relative rotative movement between the two parts.

Although the aperture A preferably comprises a relatively small square opening upon which the light beam is concentrated as a luminous spot, as an alternative arrangement the opening may comprise a narrow vertical slot. If the aperture A comprises a slot, use is made of an additional slotted aperture plate 54 preferably positioned adjacent to the plane of the aperture image, indicated by dot and dash lines in Fig. 2. The plate 54 is positioned with the slot extending perpendicular to the image of the elongated aperture A.

When employed with the optical arrangement indicated in Fig. 2, the slot of the plate 54 extends parallel with the axis of the spindle and normal to the axis of the drum D so that the successive images of the elongated aperture in the plate P angles. By this use of perpendicularly arranged slotted apertures compensation is made for undesirable motion of the drum D, for example such motion as might be caused by slight axial motion either of the disc D or of the shaft of the motor I1. Suitable means may be provided if desired to alter the width of the slot in the plate 54. A typical means for obtaining this result is shown in Fig. 11, and comprises a pair of sliding portions 55, the beveled edges of which form the slot. The sliding portions 55 are operable as by means of a thumb-screw 56 and lead screw 51 having right and left hand threads for engagement with lugs 60. The screw 51 is rotated in order to obtain the proper slot width, or to widely separate the portions 55 as will be described.

As shown in Figs. 1 and 2, the plane mirror [3 is mounted closely adjacent to the condensing lens I l and to the disc D so that the beam B issuing from the lens H may be reflected upwardly The flywheel 50 may traverse the slot in the plate 54 at right of the mirror 13 may be necessary in tain optimum operating conditions.

upon the periphery of-the disc Dffrom which 5115* cessive images of the aperture in the plate'P are formed in the plane of the plate54. Manipula'e tion of the lens I l and adjustment'of the position order to obv I V 'I'he-mir'ror l3 which is preferablyof the first-surface type is mounted for vertical and angular adjustment.

For simplicitys sake, the mirror adjusting means is illustrated in Fig. 1 as consisting of four threaded posts 58, secured in any convenient manner'to the plate 54.- Adjustment nuts 59, threaded on [the posts 58, are employed to fix the mirror in the adjusted position. e

The plane in which the image of the aperture :A (or optionally'the vertical slot) is formed may vary somewhat.

However, the image plane pref,- erably should not be located'upon orsubstantiallyupon a tangent plane or" the drum '1) or upon the oscillating mirror 21 as under these conditions the scanning effect becomes negligible. Under any one set of operating conditions the images of the aperture A preferably are formed in a fixed and predetermined plane. Accordingly, lenses BI, 62 and 63 of different focal lengths may be operatively' mounted upon a turret 64, anyone of which maybe swung into operating position to project the complete image upon the screen S to any one of several desired sizes. Suitable indexing means, as for examplea spring 65, may be employed to cooperatewith' suitably positioned notches or apertures 66 formed in the turret 6 4, as shown in Fig. 1. In this manner the spring may be lifted momentarily and substitution of the projection lens effected by partial rotationof the turret 64. The turret may also be provided with an opening 61 to permit passage of the beam B when no turret lens is required.

The diagram shown in Fig. 2 is illustrative of one preferred optical arrangement which may be employed with apparatus as shown in Fig. 1. The mirror I3 and the lens system II are adjusted until an image of the aperture A is formed between the disc D and the oscillating mirror 21, in the plane indicated by dot and dash lines. If an elongated aperture A is employed, a slotted plate 54 is interposed in the path of the beam substantially coincident with the image plane, and with the slot extending perpendicularly to the image of the aperture A. The slot width is then adjusted by turning the thumb screw 56, until the emergent beam is of approximately square cross-section. The necessary adjustment is made upon the frame scanning mirror until the desired scanning motion is produced, and the projection lens moved to the proper focus, or the turret 64 is rotated until an image of the desired size is formed upon the screen S.

Modified optical arrangements are shown in Figs. 3, 4 and 5. In Fig. 3, the image of the square aperture A is formed directly upon the screen S by a lens II, having the proper focal length. If

a turret 64 is employed, it is indexed until the opening 61 is aligned with the beam B. The lens H is then moved while the disc D and mirror 21 are stationary until the aperture is properly focussed on the screen. If this, or the following arrangements are employed with apparatus as passage of the beam B,

Idisc Dfglid oscillatingmin'or 21, after which a supplementary lens- 68 forms an image of the aperture A in space between the mirror 21 and the screen S when the disc D and mirror 2'! are stationary. If a sliding ground glass or other translucent sheet 69 is positioned in the plane of the image in space, it, serves as a monitoring screenupon which a complete picture is formed, I

lens .H is adjusted to form an image of the. aper- .ture A in space between the screen S and the mirror 21 rather-than between the disc D and the mirror 21. With this and the previously described arrangement, a monitoring screen 69 may be employed to form a small-.-size complete picture to aid the operator in the adjustment of the parts. .A projection lens 28, forms the large picture upon the screen S. V j

The mirror 21 in common with the mirror 13 and the surfaces 26, is preferably of the first-surface type. While various types of cams have been illustrated to show the manner in which the mirror 21 may be made to .follow in predetermined motion, it is to be understood that the mirror 21 may comprise the oscillating'reilector of an electro-magnetic oscillograph apparatus the opera:-

tion of which is wellnknownl In "this'manner it is possible by operating such an ,oscillograph with the desired wave form to produce a corresponding 'motionin the frame scanner. The motors E and I! are preferablymounted resiliently upon the supporting structure. g 7 I I This application is a division of our prior application Serial No. 154,218, filed July 17,1937, now Patent 2,163,538, granted June 20, 1939'. 4 N f Various other modifications may be made with} out departing from the spirit and scope of the in]- vention as we contemplate any form of construction properly within the scope of the appended claims. v

1. In a driving mechanism ior'anfoscillatable scannercomprising a pivotally mounted horizontal spindle and a mirror secured to said spindle the combination including a lever extending substantially vertically from said spindle; a cam;

means for rotatingsaidcam; a 'cam ffollower'; means for urging said follower against said earn; a iollowerrod extending from said follower to said lever; an articulated connection slidably adjustable along said lever and joining said lever with said rod; a guide adjacent to said rod and slidably supporting the same; a pivotal support for said guide; and means for raisingfand lowering said support. Q I

2. In a dr vin mechanism the combinationjas claimed inclairm 1 and'includin'g means for maintaining' the rotation of said cam constanti STEWART L. CLOTHIER: v I-JIAROLDC. H E CA P. 

